1. Field
The present disclosure relates to a heterojunction bipolar transistor (HBT) and a method to make a heterojunction bipolar transistor.
2. Related Art    U.S. patent application Ser. No. 10/854,680, also assigned to the assignee of the present application and incorporated herein by reference in its entirety, discloses a self-aligned regrown emitter HBT.    U.S. Pat. No. 6,855,948, also assigned to the assignee of the present application and incorporated herein by reference in its entirety, discloses a low Vbe HBT.    U.S. Pat. No. 6,573,539 describes an HBT with a silicon-germanium base.    J. S. Rieh et al., IEEE International Electron Devices Meeting Digest, 2002 (p. 771), “SiGe HBTs with Cutoff frequency of 350 GHz” also describes a silicon-germanium HBT.    K. L. Averett et al., J. Crystal Growth, Vol. 251, pp. 852-857 (2003), “Low Voltage InAsP/InAs HBT and metamorphic InAs BJT devices grown by molecular beam epitaxy” describes an HBT structure with a low Vbe.